In Oxytricha and other hypotrichous ciliates development of a macronucleus from a micronucleus includes transection of the chromosomes, elimination of at least 90% of the unique sequence DNA, and the formation of gene-sized molecules of DNA. All RNA synthesis (except mitochondrial) occurs on these gene-sized molecules of the macronucleus, and no RNA synthesis occurs in the micronucleus. Thus, all RNA required to operate all functions of the cell are coded for by 10% or less of the unique sequences present in the complete genome of the species (i.e. the DNA of the micronucleus). We propose therefore that the gene sequences in micronuclear chromosomes are separated by long "non-genetic" spacer DNA. We propose to test this model by mapping the location of the gene-sized sequences of the macronucleus within the chromosome-sized DNA of the micronucleus. We propose several experiments to learn how micronuclear chromosomes are processed to achieve elimination of 90% of the unique sequence DNA and to form the gene-sized DNA molecules of the macronucleus. We propose to study the organization, transcription, and replication of the gene-sized molecules of the macronucleus through EM observations and mapping of nucleotide sequences.